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    <title>WebGL2 - Multiple Objects - Manual</title>
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<div class="description">
Uses a few utility functions so there's much less code.
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<canvas id="canvas"></canvas>
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<!--
This sample uses TWGL (Tiny WebGL) to hide the clutter.
Otherwise the sample would be full of code not related to the point of the sample.
For more info see https://webgl2fundamentals.org/webgl/lessons/webgl-less-code-more-fun.html
-->
<script src="resources/twgl-full.min.js"></script>
<script src="resources/m4.js"></script>
<script src="resources/flattened-primitives.js"></script>
<script>
"use strict";

var vs = `#version 300 es

in vec4 a_position;
in vec4 a_color;

uniform mat4 u_matrix;

out vec4 v_color;

void main() {
  // Multiply the position by the matrix.
  gl_Position = u_matrix * a_position;

  // Pass the color to the fragment shader.
  v_color = a_color;
}
`;

var fs = `#version 300 es
precision highp float;

// Passed in from the vertex shader.
in vec4 v_color;

out vec4 outColor;

void main() {
   outColor = v_color;
}
`;

function main() {
  // Get A WebGL context
  /** @type {HTMLCanvasElement} */
  var canvas = document.querySelector("#canvas");
  var gl = canvas.getContext("webgl2");
  if (!gl) {
    return;
  }

  // Tell the twgl to match position with a_position, n
  // normal with a_normal etc..
  twgl.setAttributePrefix("a_");

  var sphereBufferInfo = flattenedPrimitives.createSphereBufferInfo(gl, 10, 12, 6);
  var cubeBufferInfo   = flattenedPrimitives.createCubeBufferInfo(gl, 20);
  var coneBufferInfo   = flattenedPrimitives.createTruncatedConeBufferInfo(gl, 10, 0, 20, 12, 1, true, false);

  // setup GLSL program
  var programInfo = twgl.createProgramInfo(gl, [vs, fs]);

  var sphereVAO = twgl.createVAOFromBufferInfo(gl, programInfo, sphereBufferInfo);
  var cubeVAO   = twgl.createVAOFromBufferInfo(gl, programInfo, cubeBufferInfo);
  var coneVAO   = twgl.createVAOFromBufferInfo(gl, programInfo, coneBufferInfo);

  function degToRad(d) {
    return d * Math.PI / 180;
  }

  var fieldOfViewRadians = degToRad(60);

  function computeMatrix(viewProjectionMatrix, translation, xRotation, yRotation) {
    var matrix = m4.translate(viewProjectionMatrix,
        translation[0],
        translation[1],
        translation[2]);
    matrix = m4.xRotate(matrix, xRotation);
    return m4.yRotate(matrix, yRotation);
  }

  requestAnimationFrame(drawScene);

  // Draw the scene.
  function drawScene(time) {
    time = time * 0.0005;

    twgl.resizeCanvasToDisplaySize(gl.canvas);

    // Tell WebGL how to convert from clip space to pixels
    gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);

    gl.enable(gl.CULL_FACE);
    gl.enable(gl.DEPTH_TEST);

    // Compute the projection matrix
    var aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
    var projectionMatrix =
        m4.perspective(fieldOfViewRadians, aspect, 1, 2000);

    // Compute the camera's matrix using look at.
    var cameraPosition = [0, 0, 100];
    var target = [0, 0, 0];
    var up = [0, 1, 0];
    var cameraMatrix = m4.lookAt(cameraPosition, target, up);

    // Make a view matrix from the camera matrix.
    var viewMatrix = m4.inverse(cameraMatrix);

    var viewProjectionMatrix = m4.multiply(projectionMatrix, viewMatrix);

    // Our uniforms. In this case we only have one, "u_matrix" which we'll set below
    var uniforms = {
    };

    gl.useProgram(programInfo.program);

    // ------ Draw the sphere --------

    // Setup all the needed attributes.
    gl.bindVertexArray(sphereVAO);

    uniforms.u_matrix = computeMatrix(viewProjectionMatrix, [0, 0, 0], time, time);

    // Set the uniforms we just computed
    twgl.setUniforms(programInfo, uniforms);

    twgl.drawBufferInfo(gl, sphereBufferInfo);

    // ------ Draw the cube --------

    // Setup all the needed attributes.
    gl.bindVertexArray(cubeVAO);

    uniforms.u_matrix = computeMatrix(viewProjectionMatrix, [-40, 0, 0], time, -time);

    // Set the uniforms we just computed
    twgl.setUniforms(programInfo, uniforms);

    twgl.drawBufferInfo(gl, cubeBufferInfo);

    // ------ Draw the cone --------

    // Setup all the needed attributes.
    gl.bindVertexArray(coneVAO);

    uniforms.u_matrix = computeMatrix(viewProjectionMatrix, [40, 0, 0], -time, time);

    // Set the uniforms we just computed
    twgl.setUniforms(programInfo, uniforms);

    twgl.drawBufferInfo(gl, coneBufferInfo);

    requestAnimationFrame(drawScene);
  }
}

main();
</script>
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